The phonograph, or sound-recorder, is a device for permanently recording and faithfully reproducing at any time or place all kinds of sounds, including those of the human voice. The speaking phonograph was invented by Mr. Thomas A. Edison, and is a purely mechanical invention, no electricity being used. It is, however, somewhat allied to the telephone, in consequence of the fact that, like the latter, its action depends upon the vibratory motions of a metallic diaphragm, capable of receiving from and transmitting to the air sound vibrations. When a person speaks into the mouth-piece of the instrument, which will cause the diaphragm to vibrate, and as the vibrations of the latter correspond with the movements of the air producing them, soft and yielding tinfoil will become marked along the line of the groove by a series of indentations of different depths, produced by a peculiar mechanical combination, varying with the amplitude of the vibrations of the diaphragm, or, in other words, with the inflections or modulations of the speaker's voice. These inflections may therefore be looked upon as a sort of visible speech, which, in fact, they really are. If, now, the diaphragm is removed, and a cylinder turned, we have only to replace the diaphragm and turn in the same direction as at first to hear repeated all that has been spoken into the mouth-piece of the apparatus. A stylus by this means being caused to traverse its former path, and consequently rising and falling with the depressions in the foil, its motion is communicated to the diaphragm, and thence through the intervening air to the ear, where the sensation of sound is produced.